How does stress influence bad decision-making?

Portuguese and US researchers have discovered the link behind stress and bad decision-making. Their findings, published in Science, show that chronic stress freezes us into an automatic response mode, preventing us from considering potentially more suitable and beneficial resp...

Portuguese and US researchers have discovered the link behind stress and bad decision-making. Their findings, published in Science, show that chronic stress freezes us into an automatic response mode, preventing us from considering potentially more suitable and beneficial responses.

The incidence of stress in modern life is well documented. It addition to the impact it can have on our physical health, which can include anything from ulcers to hypertension, stress can also stop us from making the right decisions. When we consider the number of choices we make on a daily basis while tense and under pressure, understanding how to prevent ourselves from making bad choices could prove invaluable.

Researchers from the University of Minho in Portugal and the National Institutes of Health in the US have discovered exactly how our choices are influenced by stress. Using rats exposed to chronic stress as well as non-stressed control rats, their study examined two types of decisions: goal-orientated, where consequences are considered in the process, and automatic, which occur as a result of habit. They also looked at exchanges between the two, and specifically considered the role that chronic stress plays in decision-making.

The team used two different tasks: the first was based on training the animals to push a lever for food, and the second was to find food without the benefit of a lever. Both groups of rats responded in similar ways to the first task. It was only when the animals started to be fed in a different way that the researchers noticed a difference. The control rats gradually reduced the number of times they pushed the lever, whereas the stressed rats continued to do so, despite the lack of food reward.

According to the team, in order to make appropriate decisions, the ability to alternate between behavioural strategies is necessary. Their study showed that chronic stress biases these strategies, favouring automatic and habitual decision-making over choices based on future consequences.

Importantly, the researchers also documented changes in the brain activity of the animals during the tasks, specifically the dorsomedial striatum (DMS), which is the part of the brain associated with goal-orientated actions, and the dorsolateral striatum (DLS), which is linked to habit formation. When compared to the control mice, the stressed rats showed an atrophied DMS and an expanded DLS.

These results could prove immensely useful in related studies, such as in understanding why addictive and compulsive behaviour is often prevalent in stress-related disorders. They may also lead to new ways of dealing with the condition, particularly for people who need to make critical decisions under constant stress, such as military personnel.

Professor Nuno Sousa of the University of Minho's Life and Health Sciences Research Institute explained that the team is now concentrating on finding ways in which the decision 'switch' can be stimulated. 'We are now focusing our research efforts in unravelling the molecular and functional mechanisms underlying these findings, in order to develop in the future new strategies that can revert [this] stress-induced bias in decision-making processes.'